In double slit experiment , the distance between two slits is `0.6mm` and these are illuminated with light of wavelength `4800 Å`. The angular width of dark fringe on the screen at a distance 120 cm from slits will be

Options

A. `8 xx 10^(-4)` rad
B. `6 xx 10^(-4)` rad
C. `4 xx 10^(-4)` rad
D. `16 xx 10^(-4)` rad

Answer

A

Explanation

Angular fringe width of first minima
`theta = (2(2n-1) lambda)/(2d) = ((2n-1)lambda)/(d)`
`theta = ((2 xx 1-1) xx 4.8 xx 10^(-7))/(0.6 xx 10^(-3))`
`= 8 xx 10^(-4)` rad
Angular width `= 8 xx 10^(-4)` rad